Optical Analysis of Nanocrystalline ZnO Films Coated on Porous Silicon by Radio Frequency (RF) Magnetron Sputtering

Abstract

Zinc oxide thin films have been deposited onto porous silicon (PSi) substrates at high growth rates by radio frequency (RF) sputtering using a ZnO target. The advantages of the porous Si template are economical and it provides a rigid structural material. Porous silicon is applied as an intermediate layer between silicon and ZnO films and it contributed a large area composed of an array of voids. The nanoporous silicon samples were adapted by photo electrochemical (PEC) etching technique on n-type silicon wafer with (111) and (100) orientation. Micro-Raman and photoluminescence (PL) spectroscopy are powerful and non-destructive optical tools to study vibrational and optical properties of ZnO nanostructures. Both the Raman and PL measurements were also operated at room temperature. Micro-Raman results showed that the A 1 (LO) of hexagonal ZnO/Si(111) and ZnO/Si(100) have been observed at around 522 and 530 cm −1 , respectively. PL spectra peaks are distinctly apparent at 366 and 368 cm −1 for ZnO film grown on porous Si(111) and Si(100) substrates, respectively. The peak luminescence energy in nanocrystalline ZnO on porous silicon is blue-shifted with regard to that in bulk ZnO (381 nm). The Raman and PL spectra pointed to oxygen vacancies or Zn interstitials which are responsible for the green emission in the nanocrystalline ZnO.

Zno Nano-Stripes Synthesized using Photoelectrochemical Wet Etching Method

“…The A1(LO) Raman line-shape is very sensitive to lattice disorder in ZnO crystals, because the nonstoichiometric defects will disrupt the long range ionic ordering [21]. The disorder will induce the phonon modes near the A1(LO) on the phonon dispersion curve to be Raman active [22]. For ZnO nano-strikes, only the allowed Raman phonon modes of A1(LO) are clearly visible at 530 cm-1 for growth on Zn foil.…”

Electrochemical Self-Assembly of ZnO Nanosheetlike Structures

“…The structural characterization of the as grown samples was carried out by X-ray diffraction (XRD) measurements with CuKα 1 radiation. The optical characterization of the films was carried out by photoluminescence (PL) at room temperature with an He-Cd ion laser as a light source using an excitation wavelength of 325nm and at an incident power of 40 mW [18]. The spot was focused to 1 mm in diameter.…”